1. Field of the Invention
The present invention relates to a method and apparatus for loading and unloading railroad cars having open tops. Such open top railroad cars are commonly referred to as gondola cars. More particularly, the present invention is related to a method and apparatus for unloading open top railroad cars utilizing a hydraulic excavator mounted on tracks. Even more particularly, the present invention relates to a method and apparatus for unloading open top railroad cars employing a hydraulic excavator mounted on tracks which is adapted to be placed upon top of an open top railroad car or gondola car.
2. Brief Description of the Prior Art
Open top railroad cars or gondola cars are commonly unloaded by large mobile cranes adjacent to the area in which products removed from the gondola cars are to be transferred or stored. Such cranes are commonly located at railroad depots or unloading yards. However, it is quite common for unloading operations to be conducted at a location at which there are no mobile cranes available for unloading such gondola cars. In such situations cranes or other unloading equipment must be transported to the site. When cranes or other unloading equipment are not available, material such as cross-ties and railroad ballast must be removed by manual labor or by methods employing devices specifically designed for unloading such materials. Manual unloading is very expensive compared to unloading by machine. However, most unloading equipment specifically designed for a gondola car or other open top railroad car is also very expensive and cannot be used for purposes other than unloading a gondola.
U.S. Pat. Nos. 4,175,902 and 4,190,394 disclose an apparatus and method, respectively, for loading and unloading railroad cars. The apparatus is a mobile, wheeled apparatus or tractor having front and rear wheels movable over the ground surface and including power actuated boom structures pivotally mounted at the respective front and rear ends of the tractor. The apparatus has rubber tires and does not have tracks thereon. The tractor includes brackets or feet for supportive engagement with the upper surfaces of the car side walls and is able to climb on top of a gondola car from a position on the ground adjacent to the end of a gondola car. In the method disclosed the tractor uses the front and rear booms to raise the tractor up to the top of the gondola. The tractor has outrigger arms with attachments thereon for engaging the top of the gondola car and a front boom structure with arm members for engaging the top of the gondola car. The wheels of the tractor do not engage the top of the gondola car.
The apparatus and method disclosed in U.S. Pat. Nos. 4,175,902 and 4,190,394 requires that the entire tractor to which the power actuated boom structures are connected must be hoisted off of its wheels and into the air by the boom structures while the operator is on the tractor operating the controls. The operator of the tractor is at great risk if the hydraulic power system of the tractor were to fail because the tractor could then fall to the ground if the failure occurred while the tractor was being lifted onto a railroad gondola car. Hydraulic system failure could occur if a hydraulic hose were to burst, and the operator could be injured and equipment damaged when the tractor falls to the ground. A highly skilled operator is required since front and rear boom structures and a winch must be operated simultaneously. Furthermore, the tractor could fall into the interior of the gondola car in the event of a hydraulic system failure after the tractor is positioned on top of the car. After the tractor first leaves the ground to climb onto the gondola car, the tractor is never again supported by the wheels until it is returned to the ground; while conducting unloading operations, the tractor is entirely supported high above the ground by hydraulic systems which are subject to failure.
It is an object of the present invention to provide a safe and inexpensive method and apparatus for loading and unloading a railroad car by enabling a hydraulic excavator having tracks thereon to be positioned at the top of a railroad gondola car for unloading and loading of the gondola car.
It is another object of the present invention to provide a safe and inexpensive method and apparatus for positioning a hydraulic excavator on top of a railroad gondola car to load and unload the gondola car whereby the hydraulic excavator can be driven along the top of the car on the tracks provided with the hydraulic excavator.
It is a further object of the present invention to provide a safe and inexpensive method and apparatus for loading and unloading a railroad gondola car by enabling a hydraulic excavator having tracks thereon to be positioned and driven on top of a railroad gondola car with the tracks of the hydraulic excavator being supported by the sidewalls of the gondola car.